The North Carolina Mental Retardation and Developmental Disability Research Center (MRRC) is a diverse and coordinated program to advance knowledge concerning the etiology and treatment of mental retardation. The causes of mental retardation and developmental disabilities are multiple. The few hundred suspected or identified represent only a fraction of the total number of causes. Many moderate to severe conditions of mental retardation have biological causes identifiable with currently available technology; however, biological causes of the majority of less severe mental retardation are presently unknown. The boundary between biological and psychosocial factors in mental retardation is becoming less distinct, not only because progress in biological sciences has led to the identification of more causes, but more importantly because there is increasing awareness of the importance of the interactive influence of psychological events of biology and of biological processes on psychological consequences. This broad-based approach remains the guiding principle of the MRRC. Thus, our research programs encompass the broadest range of concepts, disciplines and methodologies, from social and behavioral sciences to fundamental molecular genetics and developmental neurobiology. While preserving this diversity, we focus much of our work on eight major areas on research emphasis: (1) early intervention effectiveness and processes, (2) family processes and interventions, (3) language, cognitive, and social processes, (4) neurohormones and maternal behavior, (5) brain development: molecular genetics, biochemistry, toxicology and pathology, (6) neurogenetic disorders including fragile X syndrome, (7) neurotransmitter pharmacology and brain function, and (8) interaction of the immune system and the brain. MRRC researchers represent diverse disciplines and university departments. The majority of MRRC research projects are conducted in two university Centers: The Neuroscience Center (UNCNC, Kunihiko Suzuki, Interim Director) and the Frank Porter Graham Child Development Center (FPG, Don Bailey, Director). The MRRC operates as an integrated program to establish an optimal interdisciplinary environment by providing an Administrative ore and four scientific core units: Information Technology (Richard Mailman, Director), Design and Statistical Computing (Market Burchinal, Director), Observational Methods (Maria Boccia, Director) and Morphology- Pathology (Kinuko Suzuki, Director). These research efforts are augmented by existing training programs in mental retardation and related fields, a State-supported Genetic Counseling Program, and a visiting lecturer seminar series. The UNC-Chapel Hill and the State of North Carolina provide extensive support to the MRRC. By efficiently coordinating specialized core support services and by providing a common administrative framework to these diverse research programs, the MRRC achieves a cost- effective means for conducting research that seeks eventual understanding, treatment, and prevention of mental retardation and developmental disabilities.